Lineman&#39;s signaling system



Feb. 5, 1935.

RT. HAMLETT LINEMANS SIGNALING SYSTEM Filed May 10, 1932 2 Sheets-Sheet attorney 3nbentor Feb s, 1935.

R. T. HAMLETT LINEMAN'S SIGNALING SYSTEM Filed May 10, 1952 2 Sheets-Sheet 2 5, Working.

Patented Feb. 5, 1935 UNITED TA-rs LINEMANS SIGNALINGYSYSTEM Robert v r." Hamlett, Jackson Heights, N. assignor to The Western Union Telegraph Company, New York," N. Y., acorporation of New York Application May10,1932,.lSerialNo. 610,446 1 6Clair'ns. (01177-352) v This invention relates to a signaling system especially adapted for linemen who may wish to signal the central ofiice or other station from any point along the line at which they may be The purpose of the invention is to provide a signaling arrangement which may utilize the same wires that are employed in telegraph circuits .without in any manner interfering with such circuits; to provide a signalingsystem. which is simple in construction, requiring practically no supervision and is dependable; also one which requires a compact and light equipment to be carried by the linemen.

, In the following description I shall accompanying drawings in whichrefer to the Figure 1 is a diagram illustrating a circuit ar-" rangement embodying my invention, and

Figure 2 is a modification thereof. The conductors for the signaling circuit may comprise a wire from any two circuits in which one is un'grounded. I may therefore employ a wire from each of two metallic circuits as illus trated in the drawings. These "two circuits may or may not be portions of two superposed sys-' tems, such as shown for instance in patents granted to R. V. Morgenstern Nos. 1,758,900 and 1,817,702. I may use one common wire of a metallic circuit and two or more grounded circuits, each grounded circuit being connected to a difierent signaling set. The lineman would then connect his portable set to the common metallic r controlled gas discharge tube 5 having the characteristic of continuing in operation after being started by application of potential to the starting electrode until it is stopped by some external means, as by opening the circuit of the anode. One type of device which may be employed for my purpose comprises a three-element thermionic gaseous discharge tube having an anode or plate 6, a cathode 7 and a grid or starting electrode 8. In this type the grid is in the form of an inverted cup composed of line wire mesh which completely surrounds the cathode. By means of a small battery 10, a negative bias is applied to thegrid which prevents the operation of the tube until a predetermined critical voltage is impressed upon I the grid. The instantrthe critical voltage is" reached, a discharge takes'place in the plate circuit of the full value produced by the battery or generator 12 which is maintained irrespective of the starting electrode-potential until stopped by some external means. The action of thetube" in continuing the discharge unaffected by the grid voltage and until the voltage of. the plate 10 is reduced or stopped, is attributed to the formation of a sheath of positive ions around the grid, usual: 1

1y only a fraction of amillimeterin thickness? which contains the entire voltage drop between the grid and'the surrounding spacer Varying the potential of the grid merely changes the thickness of this sheath without affecting the potential of the remaining space. The action 'of the grid may,

' therefore, be'liken'ed to a trigger which is effective to initiate the discharge but which has no further influence on the discharge, being thus distinguished from the usual audion grid, which exerts a "continuous influence on the discharge-through the tube. I

In the output circuit of this thermionic tube or relay is included thelocal battery or generator 12 and the winding of a neutral relay 14. The armature of the relay 14 is adapted to close a circuit which 'actuates a signal 15 that may be either J visual or audible.

The lineman carries a compact light equipment containing a suitable generator 21 of relatively high potential, which may consist of dry cells and in series'with the generator is a high resistance 23 and an inductance 24 of high value. The choke coils are inserted for the purpose of protecting against the passage of telegraph or carrier current signals from one line to the other. The resistance in the linemans set prevents any appreciable current flow and also guards against any duplex balance change in the two metallic linemans set. The grid bias on the thermionic tube is maintained at a value which will prevent the operation of the tube due. to the small potentials existing between the two metallic circuits.

The operation of the signaling system will be evident to engineers and to those familiar with circuits of this character from the above description of the-apparatus employed.

When a lineman out on the line desires to sigcircuits when they are connected through the nal the central office or other station equipped with the signal receiving apparatus, he connects the contacts or clips attached to the flexible conductors 25 of his set to the proper conductors of the twocircuits which form the pairof linesvof the signaling system, thus applying a potential of critical value to thegrid 8, thereby causing an immediate discharge through the tube which continues.in;the=1ocalon output-circuit of the tube.

7 until" the circuit is broken by the attendant at theswitch 26. This current in the local circuit .en-.

ergizes the relay 14, thus operating the signal""15:'

In Figure 2 I have illustrated: an arrange'ment n V for signaling the several stationsselectively. Sta- --I.'ha ve;described in detail the rmentsshown for the purpose of clearly. disclosing vmy inventiom-but it. will be evident to engineers that. various modifications. and changes in the tions A and B may be signaled in-the'manner-pre-"- viously described. If it'isxdesiredt'ojsignahonly station B, the lineman reduces thevoltage of his signaling battery 21 bycutting'out some ofthe cells. The grid biasing battefyi 10 at station A is v of higher voltage than that at station B. and. hence the tube 5 at station B will start upon the ap plication -o fa loweriyoltage." Accordingly when sthe lineman. has reduced the voltage of :his Sig-- naling-battery 21 .thezproper; amount, he canjsignal :station B without affecting the signal receiver at station A. 2

. gwWhen stationsA or'B are beingsignaled station Cis-not;affectedbecause thegrid and cathode f-.elements; areficonnected to, the lines in-the re--- ..verse.manner.i Consequently when. the lineman desires to signal station C he reverses the battery.

.connections' 25 of hi s'portable set 20 in: theman- =r ner indicated in dotted :lines,

..-circu it; arrangementsxmay be made within the u scopeofltheinvention. I V

1:;In azcommunication wductors; each conductor forming-one leg of sep- I' "claim:

- .arate communication circuits carrying intelligence signals terminal-apparatusincluding an electroistatically controlledgaseous discharge tube haviif l ingwits input circuit bridged between saidcon- '.-rent.. in theso'utput circuit.

. said lines due to the connection of said source.

' 4. In a communication system, a pair- 0f con- ;ductors; each conductor. forming one leg oese pecific; arrange-1 source adapted to impress apotential' suflicient to system, a=.pair of,.con-' said conductors.

tors at any desired points, said portable means including a potential source adapted to impress 10 a potential suflicient to initiate a discharge in saidtube'. I p a. communication system as defined-in 10181111 l;'.;meansijf.or interrupting the flow of our- 15 In a' communication system as defined in claim 1, an impedance element in series relation with said-potential source to thereby limit the flowofi current and prevent any disturbance in arate ucommunication circuits carrying inteliligence, signals, a plurality. of stations each provided with apparatus including a thermionic gaseous dischargewtube having its-:input circuit bridged between said. conductors .andIit s output circuit connected to an electro-responsive device, said tube beingcharacteriz'ed by continuous durirent flow in its output after starting, biasing 0 means insaid input circuit' to determine ythe startingpotential and portablemeans adapted to be bridged across said conductors at any desir ed points, said portable means including'a potential start the operation of a tube. r I

5. In acommunication as defined in-cl'aim 4, certain of'said tubes being'biase'd to different potentials,.and means'tovary thepotential o1 the potentialisource in'saidportable means. a

6., In a communication as defined in claim 4, certain ofsaid tubes being reversely connected to 

